Want a rocking speaker for your MP3 player? Instead of buying a portable speaker, make it yourself with inexpensive parts from RadioShack. Make has complete step-by-step instructions that will teach you to assemble the whole thing and install it in the cabinet of your choice.

The MonoBox amplifies your music player's output and, despite its diminutive size, can get pretty loud. The speaker can be powered by a 9V battery or you could adapt it to use a car or boat power system. One of the best things about this project is it's pretty customizable, and if you really want stereo you can make two.